You can wean directly to raw, just be mindful of the calcium/phosphorus ratios, and be sure to get organ meats (especially liver) in there as soon as you can without causing too much upset. So, after, say a week of being on raw, start introducing liver in small quantities. My vet has seen quite a few puppies that suffered from home-prepared diets that were unbalanced. I'm not sure if those were raw or cooked, or anything else about them, but you do need to do some homework first - or rotate in some pre-made raw blends that are complete & balanced, just in case. Bravo Pet Foods, Vital Essentials, Red Rock, NW Naturals are some of the pre-made blends I rotate in on occasion.
This is my favorite 'getting started' raw website:
http://rawfeddogs.org/rawguide.html
A good book is this one:
https://www.amazon.com/Raw-Natural-Nutrition-Dogs-Definitive/dp/1556439032 the author also has a facebook group, "K9 Nutrition" which is helpful. She's not hardcore raw, so it's a very flexible and supportive group.